Roll mill cover and vehicle control



July 27, 1943. BERNSTEIN 2,325,171

ROLL MILL COVER AND VEHICLE CONTROL Filed Aug. 3. 1940 INVENTOR AmamflBs-mwrm Y 249"? AT NEY Patented July27 194:?

PATENT -2, 325.1.'1'1 "PROL IQ MI LL-covEa-AND- VEHICLE CONTROL lsidor M. Bernstein; Cincinnati, Ohio, assignor t o" Interchemical Corporation, New York, N. Y.,' a f corporation of 'Ohio V I 7 Application August 3, 1940, Serial 2 i This invention relates is multi-roll mills I (Cl..83----22) which areordinarily used for grinding paints,

enamels, inks and the like, and the'invention is particularly directed to a means for preventing excessive evaporation of the volatile ,constitu- ,ents. of: thevehicle irom ,themixture being ground and the maintenance of substantially constant and uniform composition in the mixtime by providing continuous replacement of the email amount of solventunavoidably lost] during thegrinding operation p "Ordi arily dispersed pigments, inks. the 1 like are subjectedto an extremely fine grinding anddispersion by passage 7 of the; mixture througha rollmill having atleast threerollers, inwhic'h the -pigmentqisfed between the; first two rollers and then passes between. the' second and third rollerfor a second grinding before be:-

ingrem'oved as. a; paste from thethird roller by m'eans'ldf a; doctor knife, Where;;.the pigment is difficulty dispersible themillmay employ'more than three rollers-in, series so-that1- the paste passes consecutively between a large number of rollerslwbefore' finally being removed fromthe A seriousdifficultywhich has been encountered in the'milling ofp'igment in volatile vehicles, and especially in the case of the water emulsion inks and aniline inks in which the vehicle is a solution of a spirit-soluble resin in alcohol, has been the loss of volatile solvent during grinding. The result of this has been that not only a non-uniform product is produced;

but often the pigmentbecomes precipitated or agglomerated in spots and the resulting product is commercially undesirable. The most common device employed heretofore to prevent excessive solvent evaporation during suchgrinding operations 'has consisted in a hood or covering which could be placed over they grinding rolls to reduce air circulation.

However, unless sealed joints,

ject is to provide a device'which will, when used in connection with: a vmulti-roller mill, permit the, successful and eflicient grinding and-dis persion of aniline inks, especially W'ater' emulsion of aniline inks, as Well as similar dispersions ,inyolatile solvents.- Other objects will be apparent from. the'following description.

In the drawing, 1 is'a cross sectional view of the side of a three roll mill employing a cover and solventreplenisherwhich ,is. a typical em'-- bodiment of the present invention; and I a section .H which'correspcndingly {covers the rollersBand1C'.. 1 4 The, section G, :Whichis 'placed' over the feeding end oithemill,comprises? fixed covers l0. and

ll fastened to the mill frameD and a movable cover l2 fastened to the fixed cover H] by means of hin'gesIS. [In operation, the material to be ground is placed on the feed 'roller A which carries the material between itself and the sec ond roller B; 'By means of the hinged cover I2, the rollerA is easily accessible. The main purpose of the. section Gof the invention is to keep dirt out of the material being ground and to le'ssenJthe rate of solvent evaporation by pre- 7 venting large air currents from coming in conf tact with the material being ground or 'dispersed. I l

Between the section's-G and vI-I is a baffle plate M mounted'over the roller B for the purpose or packing glands are used on the hood Where it surrounds the roller axles, some solvent is unavoidable lost at theseplaces. From the practical standpoint, a completely sealed hood is not always desirable, as this involves complicated and time-consuming'labor when it is desired to clean the rollers prior to the grinding of a different pigment.

It is therefore an object of this invention to provide a simple and easily detachable apparatus for multi-roller mills which will reduce excessive loss of solvent by evaporation andwill maintain a substantially constant and uniform composition of the mixture being milled. Another obof substantially isolating the space enclosedby the section H from the section G, inasmuch as the concentration of solvent vapor in the section H is greater than elsewhere and should be held as nearly constantas possiblein order to obtain a perfectly uniform, and controlled, solids content in the finished dispersion. Also, the baffle l4 decreases the solvent loss due to-evaporation. The section H comprises an enclosure l5 to whicha movable cover It is attached by hinges l1, and a tank IB Which is provided with tubes [9 and valves 2%. The movable cover-l6 protects the product from the mill from contamination with dirt and otherforeign particles which OFFICE-3 Fig. 2 is a view-ofjtheinilltaken alongthe v might otherwise drop in the product as it is being removed from the roller C by means of a doctor blade 2|, and passed into any desired receptacle bymeans of a trough 22. Solvent, or vehicle, to be added to the material being milled, to make up for losses, is placed in the tank l8 and supplied to. the rollers B and C through the tubes [9. The rate of addition. of

by the valves 20 and is adjusted in eacli milling vention should not be limited other than as defined by the appended claims.

I claim:

1. Apparatus for controlling the solvent or ve-,

hicle concentration in a pigment dispersion during milling on a three-roller mill, which comprises, in combination, the three rollers of said H mill positioned adjacenti one another and with solvent to thematerial being milled is controlled operation to balance the loss of solvent bys evaporation.

Thepipes l9 are placed so as ws iver the solvent, by dripi n Orr-the last two rollers in the mill (rollers vIB and C) nearithe edges of the rollers wherethefn aximum vevapo-I 1 '1 By this method ration of the solvent occurs." theconcentration of solvent in the mixture being milled and discharged may be maintained l uniform. At the same time the loss of solvent by evaporation is reduced to a practical mini mum by supplying the'make-up solvent only to the last two rollers of the millv andisolating the air space immediately above these rollers from the rest of the mill. x V

Amill employing'more "than three rollers .may beprovided with a cover and make-up solvent supply and distributing system, such as isillustrated by the sectionHin-the drawing, and'this section maybe modified andextended-tocover more rollers than just the last two, with provision for supplying solvent to each roller; The essential features are that the upper surfaces of at least the last two rollers mustbe at least partlally enclosed and thatjthe make-up solvent should be supplied in continuous mall amounts,

preterably near the ends of the. rollers. The factorwhich determines. the number of rollers to be supplied with makeupLsolvent is primarily the thinness or the film of milled material which spreadson the rollers, as the solventevaporation from thinxfilmsis much-greaterthan the evapo: ration ordinarily occurring on the feed ,roller where a relatively large quantity'of unground ma terial is present. Other;variationsz will be91p parent to those skilled "in the 'artQa'n'd the in parallel axes, a, coveringsubstantially enclosing the upper surfaces of said rollers to reduce solvent evaporation from said dispersion, a bafiie placed substantially over the center roller so that theispace within-said covering and above the third roller is substantially isolated from the -.space 'above' lthe first roller, a liquid reservoir, conduits connected with said reservoir, valves in said conduits to control individually the flow of liquid to said rollers, said conduits positioned so duce solvent evaporation from said dispersion, a baffie placed substantially over the center roller so-that the space withinsaid covering and above the third roller is substantially isolated from the space above the flrst rollerya liquid reservoir mounted" on said covering, conduits connected with said reservoir," valves insaid conduits to control individually the flow of liquid tojsaid mu,

ers, said conduits positioned so that one opening saidvalves liquid is caused to flow by gravity onto said "rollers ear the ends ,thereofj whereby the solvent concentration in said dispersion is main;

7 tained uniform and constant 'throu gh'oufithe inding ration. U f

a. I ERNS'I'EINL 

